STUDY OF RADIATION-GRAFTED FEP-G-POLYSTYRENE MEMBRANES AS POLYMER ELECTROLYTES IN FUEL-CELLS

Proton exchange membranes for fuel cell applications were synthesized by pre-irradiation grafting of styrene/divinylbenzene mixtures into po ly(fluoroethylene-co-hexafluoropropylene) films and subsequent sulfona tion. Grafting of pre-existing films overcomes the problem of shaping the grafted polymer into thin membranes and makes this process a poten tially cheap and easy technique for the preparation of solid polymer e lectrolytes. The grafted membranes were characterized by measuring the ir ion exchange capacity, swelling, specific resistivity and area resi stance. Due to their thickness in the range 67-211 mu m, some of the m embranes have a considerably lower resistance than the most widely use d membrane Nafion(R) 117 (DuPont). The short-term and long-term perfor mance of these membranes was investigated in H-2/O-2 fuel cells. Thin (< 100 mu m), highly crosslinked (12% divinylbenzene) membranes show t he best performance in the fuel cells. Tests for periods of up to 1400 h were performed to examine membrane stability and the degradation of grafted membranes.